Chain saws energized by fossil fuel and electricity have been known for many years. They have been greatly improved and varied in size and horsepower through the years. Many users are amateurs and the chain saw can be a dangerous mechanism. Any provision for rendering the chain saw less harmful is obviously an important step forward in the art.
It is an object of this invention to provide, in the cutting chain itself, an improvement wherein the chain will cut a solid substance (e.g. wood) as usual, but without any attention on the part of the user, will minimize its tendency to cut soft tissue (such as flesh). The safety feature is built directly into the chain.
Articulated chain for a chain saw generally includes a plurality of successive links which are pivotally interconnected to allow them to ride first on a relatively flat, or straight, portion of a cutter guide bar, around a curved end of the bar, and then along another relatively flat, or straight, portion of the bar. The links include cutter teeth which project outwardly a preselected distance from the bar to cut material. Generally a depth gauge, or safety element, leads each cutter tooth and projects outwardly from the bar a distance somewhat less than the distance of the cutter tooth to limit the depth of cut taken by the cutter tooth.
A general object of the present invention is to provide a saw chain which is so constructed that when the chain is running on the generally flat, or straight, part of the bar, the safety element, or depth gauge, projects outwardly from the bar a distance greater than the cutter tooth when the chain is not in engagement with hard material (such as wood to be cut), but is able to be urged inwardly toward the bar to expose the cutting edge of the cutting tooth for cutting as the chain is pressed against the hard material. In this way the chain provides a safety feature whereby soft tissue or material, such as flesh, will be protected if it comes in contact with the chain since it will not overcome the force required to press the safety element down toward the bar, whereas on operation to cut harder materials, such as wood, it can be pressed toward the bar to expose the cutting edge.
More specifically, an object of the invention is to provide safety chain in which a cutter element has forward and rearward pivot connections and is so constructed that when the chain is tensioned (as occurs when the chain is driven around the bar), and running along the flat portion of the bar without pressing against a hard material, and the pivot connections are substantially in line, the underside of a forward portion of the cutter is spaced from the bar and the safety element, or depth gauge, associated with the forward end of the cutter is held at its higher position. When the chain is pressed against a harder material to be cut, the depth gauge is pressed toward the bar to expose the cutter.
An object of the present invention thus is to provide a novel safety chain which is constructed to minimize its tendency to cut softer material, such as flesh, but is operable when pressed against harder material to provide effective cutting of such harder material.